Method of making plate and fin heat exchangers



April 16, 1968 H. c. GERSBACHER 9 5 METhOD OF MAKING PLATE AND FIN HEAT EXCHANGERS Filed Oct. 22, 1965 2 Sheets-Sheet 1 INVENTOR I )6 1 ATTORNEY April 1968 H. c. GERSBACHER 3,377,684

METHOD OF MAKING PLATE AND FIN HEAT EXCHANGERS Filed Oct. 22, 1965 2 Sheets-Shee 2 A? INVENTOR MM fl/Mey c. 6,? 58/90/52 /O 7 1: 1 V I I 3 Jr a i l 26 L "-wlEA/VMVVVQ BY /0 /2 n- Ki r ATTORNEY United States Patent 3,377,684 METHOD OF MAKING PLATE AND FIN HEAT EXCHANGERS Harry C. Gershacher, Dayton, Ohio, assignor to United Aircraft Products, Inc., Dayton, Ohio, a corporation of Ohio Filed Oct. 22, 1965, Ser. No. 501,400 10 Claims. (Cl. 29157.3)

This invention relates to methods of heat exchanger manufacture, and particularly to the fabrication of plate and fin type heat exchangers.

A popular method of joining together the parts of a device as described is by brazing. The parts are assembled or stacked" in a fixture and then brazed according to any of the usual techniques to bond contacting parts with one another and thereby create a unitary structure. The fixture customarily provides a rectangular outline opening receiving the stacked parts. This is the conventional configuration of plate and fin heat exchangers. Accordingly, when the need arises to build a heat exchanger core of non-rectangular configuration, or one smaller in its dimensional outlines than the rectangular outline of existing fixtures it is necessary to provide special fixtures adapted to receive and hold the heat exchanger core or special shape. This is, of course, an undesirable recourse since it adds substantially to the cost of manufacture, and may involve the keeping on hand of numerous fixtures of varying design and shape and which may never be used a second time.

It is the object of this invention to obviate problems of the prior art in this regard, it being proposed to enable all heat exchanger cores to be assembled and held for brazing in a standard fixture of rectangular shape, whether or not the outline configuration of the desired core is of the same rectangular shape as the fixture.

Another object of the invention is to achieve the foregoing without adjustment or modificaiton of the fixture.

Other objects and structural details of the invention will appear from the following description, when read in connection with the accompanying drawings, wherein:

FIG. 1 is a partly diagrammatic view of the parts of a heat exchanger core stacked in a fixture in accordance with one method step of the invention;

FIG. 2 is a fragmentary plan view of a plate or parting sheet used in the assembly of FIG. 1;

FIG. 3 is a fragmentary view of the core of FIG. 1, shown in a subsequent method step in accordance with the invention;

FIG. 4 is a fragmentary view showing the core segment of FIGURE 3 as received by manifold means;

FIG. 5 is a view in cross section, taken substantially along the line 5-5 of FIG. 2; and

FIG. 6 is a detail view of the core of FIG. 1, relatively enlarged.

A plate and fin heat exchanger of the kind to which this invention relates is comprised essentially of but three elements, plates, sometimes referred to as parting sheets, strip fin material, and elongated spacers in the form of bars or channel pieces. The plates are superposed one upon another, the strip fin material is placed between adjacent plates and the spacer members are marginally disposed between the plates at side edges thereof in a manner to define passageways for different fluids which achieve a heat transfer relation through the separating plates. The strip fin material is disposed in the passage ways. It provides secondary heat transfer surface, and, in addition, binds together and supports adjacent plates.

In the illustrated instance plates 10 occupy a vertically spaced superposed relation to one another. Strip fin material 11 is disposed between adjacent plates and 3,377,684 Patented Apr. 16, 1968 "ice channel pieces 12 and 13 provide the aforementioned marginal spacer means. The channel pieces 12 and 13 are or may be identical except that in the illustrated instance the spacers 12 are larger than the corresponding members 13. The parts further have been distinguished from one another since the spacers or channel pieces 12 are disposed to extend longitudinally in one sense while the spacer bars or channel pieces 13 are disposed to extend longitudinally in a sense at right angles to the direction of the members 12. Each pair of spacers 12 in the same plane define a through passage 14 in which strip fin material 11 is disposed. Each pair of channel pieces 13 similarly define a passageway in adjacent relation to the passageway 14 but at right angles thereto, and, in the illustrated instance, of lesser height than the passage 14. There may be disposed in the second described passage other strip fin material like the material 11. A fluid flowing through the passages 14 is thus in a heat transfer relation, through the intermediate plates, with a fluid flowing through the passage defined by channel pieces 13. In the example here shown the relatively large passages 14 are adapted for flow of a coolant such as air therethrough while the relatively smaller passages 13 fioW a liquid to be cooled therethrough, for example oil. Thus the device as shown may be an air-oil heat exchanger. The arrangement is, of course, of substantially universal use in the modifying 0f the temperature of one fluid by reference to the temperature of another fluid, both fluids being put through the heat exchanger in a segregated, heat transfer relation as described. The device as shown in FIG. 1 is essentially a core. Manifolds are suitably applied thereto to control the flow of at least one of the fluids. For example, manifolds may be applied to the core to control the flow of either one or both of the fluids passing therethrough.

In the assembly of a heat exchanger core as described above, the parts are stacked as described in a fixture 15 providing a central rectangular opening 16 to receive the core. Individual components are stacked or placed in a superposed relation upon one another as described, beginning at the bottom of opening 16 with a plate 10. On this, as seen, is placed a pair of laterally spaced apart channel pieces 12. Between the spacers 12 is installed a length of the strip fin material 11. Overlying the channel pieces 12 and strip fin material 11 is a pair of laterally spaced apart channel pieces 13 arranged at right angles to the channel pieces 12. However, there is disposed be tween the channel pieces 13 and the underlying assembly comprising channel pieces 12 and strip fin material 11 another plate not identified and not illustrated in FIGS. 1 and 3 but shown at 20 in FIG. 6, which plate serves to separate the passage 14 defined by channel pieces 12 from a similar passage defined by and between the channel pieces 13. The scale of the parts in the drawing is too small adequately to show the plate in question in FIGS. 1 and 3. Over the channel pieces 13, between which a fin strip may be installed, as before described, is placed another plate 10 and the stacking of parts is continued in this manner until the opening 16 in the fixture 15 has been filled.

All of the parts thus far referred to are made of a heat conductive material lending itself to a joining with like parts in the brazing or like operation by which the parts are united. Commonly, the parts are made of an aluminum alloy for weight conservation, or of stainless steel or the like when strength factors are important. In the illustrated instance the heat exchanger core is constructed with a view to lightness in weight, being adapted for use in the aerospace industry. Thus, the strip fin 11 is made of a thin, ductile material readily lending itself to gathering in the crimped configuration shown. The spacers 12 have a channel shape in order to reduce weight and in order to preserve the concept of thinness of adjacent, contacting parts so that thermal shock in the brazing process may be avoided. The parting sheets or lates interposed between the channel pieces 12 and 13 are constructed to be sufiiciently heavy to lend rigidity to the assembly but to be sufficiently thin for gOOCl bonding to contacting parts 11, 12 and 13 and to be capable of efiicient heat transfer.

Considering further the plates 10, at least some of these have laterally spaced apart tabs 17 and 18 projecting upward from one surface thereof. While the tabs may be in the form of separate devices fastened to the plates, or may be detents formed integrally with the plates they are in the illustrated instance outstruck as tongues from the material of the plates. There are one or more longitudinally spaced apart tabs 17 (in the present instance two) and a corresponding number of tabs 18 aligned with corresponding tabs 17. The tabs are spaced inwardly from side margins of the plates and are spaced apart from one another selected, predetermined distances as Will hereinafter more clearly appear.

In accordance with the invention, therefore, all of the plates are of the same size and are dimensioned to be closely received within the opening 16 of the fixture 15 with their side margins engaging side walls of the fixture. Where the desired outline of the heat exchanger core differs from the rectangular outline of opening 16 plates 10 with their tabs 17 and 18 are selected and positioned in a pattern to produce the desired configuration. In the instance shown in FIG. 1, the desired outline of the heat exchanger core is a generally cylindrical one. Thus the lowermost plate 10 or the one first placed in the fixture 15 has tabs 17 and 18 spaced apart a minimum distance. The next plate 10, or pair of plates, provides tabs 17 and 18 of somewhat greater spacing and this continues in progressive step by step fashion until the mid portion of the heat exchanger core is reached where plates 10 are employed having no tabs 17 and 18. In these instances the channel pieces 12 are placed at the margins of the plates in the conventional manner of plate and fin heat exchangers. Beyond and above the mid area of the core plates 10 are selected which again are formed with the tabs 17 and 18, these being plates of maximum distance between the tabs. In progressive steps plates 10 are used of lesser spacing, ending in another plate 10 of minimum tab spacing like the one first installed in the fixture. The tabs 17 and 18 provide stops accurately positioning the channel pieces 12 and thereby the strip fin material 11 installed between the channel pieces. The plates 10 are used in some instances in groups of two and three, as regards the spacing between the tabs 17 and 18 in order to achieve the desired configuration. The cylindrical pattern defined by the tabs 17 and 18 is in a peripherally stepped form. At each step, below and above the central area of the core, the plates 10 extend in a projecting relation to the tabs 17 and 18. Installed between the projecting portions of adjacent plates 10 is other strip fin material 19, the fin material 19 extending from the tab 17 or 18 outwardly to the marginal edges of the plates 10.

The strip fin material 19 serves a purpose in supporting outer projecting portions of the plates 10 in such a manner that a firm clamping of the assembly within the fixture 15 is possible. After the core has been stacked or assembled within the fixture any necessary adjustment of the of the fixture is made to clamp the parts together and hold them in the relative positions as shown in FIG. 1. Following this the assembly is subjected to a process uniting contacting parts of the assembly with one another. According to a popular method of joinder the assembly is subjected to a brazing process, as by being heated in a furnace or by being dipped in molten flux, Following this method step, and after the core has cooled and been removed from the fixture 15, the projecting portions of the plates 10, beyond tabs 17 and 18, are removed, along with the interposed strip fin material 19 and the projecting portions of the channel pieces 13. This may be done by a cutting or like process by which the tabs 17 and 18, along with all material outwardly thereof, including the material 19, the plates 10 and channel pieces 13, is detached or taken away from the core proper, This leaves a generally cylindrical structure, having a stepped periphery wherein the channel pieces 12 and the severed edges of the plates 10 and channel pieces 13 define the sides of the core. The resulting structure is as shown in FIG. 3.

A heat exchanger core constructed as shown has a general utility. It is commonly used, however, in connection with manifolds applied to control either one or both of the fiuids flowing through the heat exchanger. For example, as shown in FIG. 4, a circular manifold 21 may be placed in surrounding relation to the core in a manner to effect a controlled communication of the interior of the manifold with the passages defined by the channel pieces 13. The core is indicated diagrammatically at 22 in FIG. 4 as being received in the circular manifold 21.

Various features and aspects of the invention will be apparent from the foregoing. For example, it is to be noted that the assembled core as received in the fixture 15 has generally the same construction outwardly of the tabs 17 and 18 as it does inwardly thereof. Accordingly the reception of the core within the fixture and the clamping thereof by the fixture is in all respects a usual and conventional one. The core thus is held and brazed in the usual manner. The interposed stops provided by the tabs 17 and 18, however, provide a distinct and calculated pattern whereby the resultant desired core is readily achieved and has the precise required configuration.

The strip fin material 19 is desirably, although not necessarily, made of a material different from that of the plates 18 and other parts of the heat exchanger core. This preeludes effective brazing between these parts and facilitates the cutting away process which follows brazing. The use of strip fin material to support projecting portions of the plates may be unnecessary since other insert devices could be installed for this purpose. However, in dip brazing the fin material obviates problems of unequal heating and cooling, and, moreover, allows the molten flux to drain readily from the core when it is lifted from the flux bath.

Further, it will be understood that heat exchanger cores with varying configuration may be produced by the instant method. By a proper selection and arrangement of plates 10 with differentially related tabs 17 and 18, any desired pattern within the confines of the fixture opening 16 may be achieved. These include not only the non-rectangular forms, such as shown here, but rectangular configurations which are less than that of the opening 16. A single fixture 15 thus may without any change in its own structure be used in the fabrication of heat exchanger cores of varying shape. The plates 10 are lanced or otherwise punched to form the tabs 17 and 18. The tabs are variously located, in accordance with predetermined dimensions and the plates of varying tabular distance selected to achieve the desired pattern. In the placement of the plates 10 in the assembly, those plates above and below the center area are relatively inverted in order that the top and bottom surfaces of the core may be flat.

The channel pieces 13 and plates 20 extend, like the plates 10, to the side walls of opening 16, and are removed, along with the projecting portions of such plates, in arriving at the final core configuration.

What is claimed is:

1. A method of making a generally cylindrical plate and fin heat exchanger using a fixture for assembly thereof having parallel sides, including the steps of providing a plurality of equal size flat thin plates having parallel sides, some of said plates having on a surface thereof laterally spaced apart stops, the stops of some plates being differentially spaced as regards corresponding stops on other plates, said stops being located inwardly of adjacent side edges of said plates, using said plates in the assembling of a heat exchanger core in said fixture wherein appropriately sized strips of fin material are installed between said stops on respective plates, side margins of said plates projecting beyond said fin strips to engage sides of the fixture, joining together contacting parts of the heat exchanger core while it is held by said fixture, releasing the core from said fixture, and removing projecting side margins of said plates including said stops.

2. A method according to claim 1, characterized in that in the assembling of the heat exchanger core said plates are stacked in a superposed relation with lowermost and uppermost plates being plates of minimum spacing between stops and intermediate plates toward the center of the core being plates of progressively greater spacing between stops.

3. A method according to claim 1, characterized by the further step of installing between projecting side margins of adjacent plates outwardly of the stops other strip fin material during the assembling of the heat exchanger core, said other strip fin material serving to support said plate margins and being removed therewith in said removal step.

4. A method according to claim 1, characterized in that said stops are formed by striking integral tabs from the plane of said plates at selected locations thereon.

5. A method according to claim 1, characterized by the further step of installing in the assembling of the heat exchanger core nose pieces to limit against said stops whereby to define with adjacent plates a passage through the core, said strip fin material being received in said passage, the removal of the marginal side edges of said plates exposing said nose pieces to form in part the sides of the heat exchanger core.

6. A method of using a conventional rectangular fixture to assemble and brazc together a plate and fin heat exchanger of special non-rectangular configuration, including the steps of stacking in said fixture rectangular plates of a size to contact and to be held by the sides of said fixture, there being laterally spaced apart stops on at least some of said plates projecting upward from a surface thereof and located inwardly of said margins of the plate, the spacing of the stops on said plates being variable and predetermined and the order of stacking of said plates being selected to produce an outline of stops in the desired non-rectangnlar configuration, assembling with said plates other parts of the heat exchanger core including fin strips installed between spaced stops on each plate, subjecting the assembled parts to a brazing operation, releasing the brazed core from said fixture and removing laterally projecting portions of plates having said stops outwardly of and including said stops.

7. A method according to to claim 6, characterized in that said stops are formed by striking tabs from said plates upwardly, out of the material of the plates at predetermined locations thereon.

8. A method according to claim 6, characterized by the further step of installing other fin strips between projecting marginal portions of plates having stops inwardly of their side edges, said other fin strips being made of a material different from that of said plates and being removed with removal of said marginal portions of said plates.

9. A method of using a fixture to assemble and bind together the parts of a plate and fin heat exchanger core, which core has a configuration not conforming to the area outline defined by said fixture in which said core is assembled, including the steps of stacking plates in said fixture conforming in side to side dimension to the said area outline thereof, providing stops on those plates at locations where the core configuration is less than the said side to side dimension of said plates, said stops being spaced inwardly of side margins of their plates preselected distances, cornpleting the assembly of said core including the installing of fin strips between said stops, binding the parts together, and removing projecting side margins of said plates.

19. A method of fabricating a plate and fin heat exchanger core, wherein plates, strip fin material and marginal spacers are stacked in an assembled relation and then joined in an integral unit; characterized by a use of plates all of equal size but certain of which have raised stops providing abutment for said marginal spacers short of side margins of said certain plates, said plates being selected and positioned to form a pattern of spacer location which is at least in part in spaced inward relation to the side margins of the plates, projecting portions of the core outside said pattern being removed after joinder of the parts.

References Cited UNITED STATES PATENTS 2,778,606 1/1957 Lloyd et al. 165-449 X 2,865,613 12/1958 Egenwall et al. l-l67 2,959,401 11/1960 Burton 113-118 X 3,305,010 2/1967 Campbell et a1 l65-166 JOHN F. CAMPBELL, Primary Exan'ziner.

D. C. REILEY, Assistant Examiner. 

10. A METHOD OF FABRICATING A PLATE AND FIN HEAT EXCHANGER CORE, WHEREIN PLATES, STRIP FIN MATERIAL AND MARGINAL SPACERS ARE STACKED IN AN ASSEMBLED RELATION AND THEN JOINED IN AN INTEGRAL UNIT; CHARACTERIZED BY A USE OF PLATES ALL OF EQUAL SIZE BUT CERTAIN OF WHICH HAVE RAISED STOPS PROVIDING ABUTMENT FOR SAID MARGINAL SPACERS SHORT OF SIDE MARGINS OF SAID CERTAIN PLATES, SAID PLATES BEING SELECTED AN POSITIONED TO FORM A PATTERN OF SPACER LOCATION WHICH IS AT LEAST IN PART IN SPACED INWARD RELATILON TO THE SIDE MARGINS OF THE PLATES, PROJECTING PORTIONS OF THE CORE OUTSIDE SAID PATTERN BEING REMOVED AFTER JOINDER OF THE PARTS. 